Protect against FilerException

[scoheb]

If an annotation processor is called more than once, you may receive a FilerException.

This protects against that case.

[olivergondza]

This change is undesirable

[olivergondza]

Can you attach said build failure stacktrace?

[scoheb]

Here is a stack trace:

[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] javax.annotation.processing.FilerException: Attempt to reopen a file for path /home/shebert/work/jenkins/plugins/ath-test/target/test-classes/META-INF/annotations/org.jenkinsci.test.acceptance.docker.DockerFixture
[ERROR] javax.annotation.processing.FilerException: Attempt to reopen a file for path /home/shebert/work/jenkins/plugins/ath-test/target/test-classes/META-INF/annotations/org.jenkinsci.test.acceptance.docker.DockerFixture
[INFO] 2 errors

I added a test case here: https://github.com/scoheb/ath-test

Simply do a mvn clean install

[olivergondza]

Looks good to me otherwise. @kohsuke, can you?

[olivergondza]

@kohsuke I have forked this under https://github.com/jenkinsci/cucumber-annotation-indexer so we all can improve it. I consider that to be the upstream now.